A rotor assembly for an electrodynamic machine is provided. The rotor assembly comprises a lamination section and an end connector. The lamination section comprises rotor lamination sheets formed to define an annular array of axial cooling ducts mechanically supported by a plurality of radial and arched structural members that define an array of arched or angled supports to readily pass a magnetic flux via an optimal flux path. The lamination section further comprises rotor slots, with rotor conductor bars being disposed in the rotor slots. The end connector is supported by the rotor conductor bars. An axial space is formed in the lamination section by the annular array of axial cooling ducts for guiding a cooling fluid flow in an axial direction through the rotor assembly.